Conventional drive systems usually have backlash, meaning that the motor of the drive system can move without the output of the drive system moving. Backlash can make controlling the motion of the drive system's output difficult.
Various drive systems of been developed that minimize backlash. Perhaps the most common example of these drive systems is the harmonic drive. Unfortunately, harmonic drives are usually expensive and relatively large. Another drive system developed to minimize backlash incorporates so-called “anti-backlash” gears, as shown in FIG. 1. In an “anti-backlash” gear design, the gear is split into two halves that are coupled with springs. The springs are preloaded so that when the “anti-backlash” gear meshes with a regular gear, the two halves of the “anti-backlash” gear rotate relative to each other to take-up any backlash in the mesh. Unfortunately, this design may only be suitable for transmitting relatively light loads, as only one of the two halves may be fixed to a shaft. As a result, when the load is transmitted to the gear half that is not fixed to the shaft, it must be transmitted to the gear half that is fixed to the shaft through the springs. A load that exerts a higher force on the springs than their preload causes the backlash to reappear. Another drive system developed to minimize backlash is shown in FIG. 2. A first motor drives a rack in a desired direction, while a second motor drives the rack in the reverse direction but with less force than the first motor. The motors “fighting” each other provide a preload and take up backlash. Unfortunately, this design reduces the efficiency of the system due to the two motors constantly working against each other. Both motors may also need to be controlled simultaneously, increasing the complexity of the controller.
There is a need for a drive system that minimizes backlash while being cost-effective, efficient, and able to carry higher loads.